This invention relates to a process for the production and recovery of hydrocarbon chemical feedstocks and hydrocarbon fuels from renewable plant sources using whole plants.
In the prior art, industrial, farm and household wastes have been taught as sources for recovery of organic compounds by heating in the presence or absence of oxygen. The presence of oxygen causes the reactor product to contain significant amounts of carbon dioxide and water. If oxygen is not used to maintain combustion, an indirect method of heating typically is used with consequent problems of heat transfer. For example, U.S. Pat. No. 3,639,111 teaches a method and apparatus for destructively distilling kraft black liquor, garbage, and organic wastes at an elevated temperature and a controlled amount of oxygen insufficient for complete combustion, the elevated temperature being above a critical temperature zone, thereby reducing or cracking gases from the material to stable end products, the temperature being maintained to preclude recombination of intermediate products. The cracking products are hydrogen, carbon monoxide and methane. Sulfur compounds are scrubbed out as hydrogen sulfide. U.S. Pat. No. 3,718,446 teaches the pyrolysis of kraft black liquor, garbage, and organic wastes at a sufficiently high temperature (of 800.degree. C. to 1,200.degree. C. or higher) and for a sufficient length of time (of from 1 to 30 seconds) to prevent recombination reactions and produce stable products such as aromatic phenols, hydrogen, carbon monoxide, carbon dioxide and methane. Gaseous emissions from the pulping operation are the source of oxygen. U.S. Pat. No. 3,729,298 teaches a process for disposing of solid refuse by thermally decomposing it in a shaft furnace with temperatures on the order of 3000.degree. F. and simultaneously producing a fuel or synthesis gas primarily containing over 50% carbon monoxide by combusting the char and hydrogen. A gas containing at least 40% oxygen is fed into the furnace to create a thermal driving force in excess of 1600.degree. F. A reducing atmosphere in the hearth is taught to prevent over-oxidation of the char to CO.sub.2 and oxidation of the metallic components of the refuse although the process can be operated under mildly oxidizing conditions. U.S. Pat. No. 3,843,457 teaches a process for microwave pyrolysis of wastes to recover vaporizable organic compounds such as organic acids and aldehydes from nominally solid organic wastes by comminuting the wastes and mixing them with a gas stream at a pressure substantially less than atmospheric. The gases are preferably reducing gases, particularly hydrogen. The comminuted wastes are subject to microwave discharge which effects molecular decomposition and the vaporized components are thereby removed from the gas stream. U.S. Pat. No. 3,983,009 teaches the destructive distillation of solid organic wastes to reduce volume and produce usable products such as oils, pyroligenous liquor, methanol, acetone, combustible gases, and a high carbon char without environmental pollution. The hot gases are fractionally distilled to remove useful products and are then recycled into the destructive distillation process with additional combustion air. U.S. Pat. No. 4,002,438 teaches a method and a device for the flash pyrolytic conversion of organic materials into gaseous or liquid fuels comprising methane, hydrogen, ethane with some light oil fractions in a single self-contained vessel wherein problems of clogging, coke formation, and sludge formation are substantially avoided by use of a mixture of dense, hard abrasion-resistant material which is recycled with recycled product gas and combustion air. U.S. Pat. No. 4,078,973 teaches a closed loop pyrolysis process for organic solid wastes wherein the heat is supplied by inert particles which are heated in a separate combustion zone. The residence time during pyrolysis is generally less than 10 seconds. The pyrolysis temperature is between 600.degree. F. and the introduction temperature of the inert particles to the pyrolysis zone which can be between 600.degree. F. to about 2,000.degree. F. The carrier gases are oxygen-free. The products are carbon-containing char, pyrolytic oils of an oxygenated nature and gases primarily of the oxides of carbon and light hydrocarbons. U.S. Pat. No. 4,153,514 teaches a process for recovery of chemical values from waste solids wherein shredded waste solids are intermixed with hot char and a carrier gas and passed through a pyrolysis zone under turbulent conditions at temperatures of from 300.degree. F. to 2000.degree. F.
It is known also that pyrolysis of municipal waste containing cellulose can produce olefins. When finely divided cellulose-containing waste is rapidly heated to 700.degree. C., olefins are reported as being the dominant product with a relatively dilute system and short residence times. Aromatic tars or oxygenated organics form if the reaction continues (Chemical & Eng. News, Oct. 1, 1979, p. 37).
In the prior art, processes have been taught for recovery of hydrocarbons from sources other than waste materials. The crushing of oil seeds to obtain vegetable oils is well-known as is also the distillation of pine stumps to obtain naval stores. Crushing combined with water extraction as well as catalytic processes are known. For example, U.S. Pat. No. 1,740,079 teaches the extraction of rubber from plants such as guayule. The guayule plants are reaped and dried, then crushed by rolls or other suitable machinery so as to open up the pith seams and break the bark. The crushed plants are cut into short pieces and soaked in water until the bark and pith are soft. The entire mass of material is then introduced into a water-filled ball mill and subjected to the action of such mill until the bark and pithy material are separated from the hard woody material. The bark and pithy material are reduced to a pulp. The rubber particles are freed from the rest of the material and are agglomerated to rise to the surface of the water for removal. As for processing the rubber from the guayule plant, it has been reported (Chemical Engineering, May 8, 1978, p. 100) that a major problem is that about 25% in unwanted resins normally comes out with the raw rubber. Another extraction process for recovering hydrocarbon values from whole-plant feedstock crops employs rolling mills that shear and compress plant material between dissynchronous rollers. The action of the rollers ruptures cellular material to facilitate downstream extraction with solvents in contrast to the conventional process in use which is wet milling (Chemical Engineering, Sept. 11, 1978, p. 101). Catalytic processes also have been developed. Hydrolyzed wood chips are converted directly to an oil by means of a sodium carbonate catalyst and biomass is converted to hydrogen, carbon monoxide and olefins to paraffinic fuels by use of a Fischer-Tropsch-type catalyst (Chemical & Eng. News Oct. 1, 1979, p. 35). Methods have been suggested to recover certain useful hydrocarbons from plant crops such as solvent extraction of organic materials (Science, 198, Dec. 2, 1977, 942-944), pyrolysis of tree bark to obtain benzene compounds (Tr. Sib. Tekhnol. Inst., 1970, No. 43, 30-33; CA77:90240v), hydrolysis of carbohydrates in plant biomass to sugars for further processing (Chemical & Eng. News, Apr. 3, 1978, 31).
Accordingly, the prior art teaches processes wherein solid waste and waste products are used as sources of organic compounds, by decomposition, by cracking or by destructive distillation. Crushing and extraction processes have also been taught. However, prior art processes have not dealt with the problem of obtaining hydrocarbons from hydrocarbon-containing plants wherein the said hydrocarbons are recovered from a crop in liquid and gaseous form suitable for use as fuel or as chemical feedstocks.
An object of this invention accordingly is to provide a process for production of chemical feedstocks and hydrocarbon fuels from plant sources which permits the effective utilization of whole plant biomass as a raw material source. Another object of this invention is to provide a process for the production of liquid and gaseous hydrocarbons from plant biomass in quantity. Another object is to provide increased production of liquid and gaseous hydrocarbons from renewable natural resources. Another object is to maximize production of liquid and gaseous hydrocarbons with value as chemical feedstocks and as fuels.
These and other objects and advantages of the present invention will become clear from the following specification.